The objective of the research project is to identify and characterize surface glycoproteins of mouse lymphocytes with the long-term goal of understanding lymphocyte differentiation and function. Monoclonal antibodies have been obtained against several mouse lymphoid tissue-specific surface glycoproteins including Thy-1 and T200 glycoproteins. These reagents are being used to study various aspects of hematopoietic differentiation in the mouse and to investigate the biosynthesis of specific cell surface molecules. Efforts to obtain monoclonal antibodies which can be used to biochemically detect surface glycoproteins restricted to specific subpopulations of mouse lymphocytes will continue. Such antibodies will be characterized on a panel of mouse hematopoietic cell lines and selected antibodies then used in genetic, biochemical and functional studies of mouse lymphocyte cell surfaces.